1. Field of the Invention
The present invention relates to a welding apparatus which can shorten a time period needed for moving a welding tip from a weld point to a successive weld point and an operation method thereof.
2. Description of the Related Art
As illustrated in FIGS. 5 and 6, a conventional spot welding apparatus has a general purpose robot 1 and a welding gun 3 mounted to a wrist 2 of the robot 1. In the welding apparatus, the welding gun has a welding tip 4 which is driven by an air cylinder.
The robot 1 and the welding gun 3 are operated according to an operation timing schedule shown in FIG. 7. More particularly, when or after the welding gun has reached a position corresponding to a welding point, a pressurizing start instruction is issued and the pressurizing motion continues for a time period t.sub.1. After pressurizing, welding starts by applying an electric current to the welding tip. After terminating the electric current, a depressurization start instruction is issued and the depressurization continues for a time period t.sub.2. When or after depressurization has finished, the welding gun moves toward the successive welding point driven by the robot.
However, the pressurizing time period t.sub.1 and the pressurizing release time period t.sub.2 lengthen the welding cycle time.